The Long Duration Balloon Project — McMurdo Station
After the more light-hearted tales of our geobears from yesterday, we are back to serious science today! My goal is to teach you about a wide variety of things related to Antarctica and this blog post, although more technical, is very interesting science! Read on!
Each austral summer, the National Aeronautics and Space Administration (NASA) and the National Science Foundation (NSF) conduct annual scientific balloon experiments, based near McMurdo Station. The Long Duration Balloon (LDB) Project workshop and launch facility are located on the Ross Ice Shelf, near the old Willy Field Runway.
Yesterday I had the opportunity to sit down and talk with Michele Limon, one of the scientists working out at the LDB facility. Michele is part of the EBEX Project, one of three projects which has launched long duration balloon experiments this season. He has been involved in two ground-based astronomy projects at South Pole Station. This is his first season at the LDB site.
Michele is a researcher from Columbia University in New York City and he works on this project with scientists from the University of Minnesota. Michele said that he was always interested in designing and building things. He first became interested in radio astronomy while studying in Milan, Italy, his home city.
Two other LDB projects this season, BLAST-Pol and the Super-TIGER Cosmic Ray Balloon Experiment, are projects from other universities around the United States. Each of the three projects has built a payload (a piece of equipment or multiple pieces of equipment) that has been launched into the atmosphere and will send back or collect data.
The “payload” is launched with a specially designed, durable, polyethylene balloon designed to carry it on a path around Antarctica. These gigantic balloons are about the thickness of a thin plastic shopping bag. The science teams track and recover the scientific experiments suspended beneath the balloons.
This season all three of the LDB projects are related to astrophysics. Here is a look at the assembly and launch site.
The LDB site has two huge building used for assembly of the experiments (remember, that’s called the payload). These buildings are on skis, just like our containers for WISSARD. There is a building for rigging the balloons, and also a communications center (the one with the two white balls on the top).
The site has bathroom facilities and a galley for serving lunch or snacks for everyone at LDB. In the photo below, they were serving Thanksgiving dinner!
Now let’s get down to the science!
The EBEX experiment will collect data about the electromagnetic radiation that’s left over from the Big Bang. This radiation was first discovered at the AT & T Labs in New Jersey by two engineers, Arno Penzias and Robert Wilson. Their serendipitous discovery took place while they were experimenting in satellite communication using radio equipment. Their scientific discovery was the most conclusive evidence supporting the Big Bang Theory up to that date. Penzias and Wilson received the Nobel Prize in Physics in 1978.
For experiments taking place in Antarctica, equipment and instruments are shipped to New Zealand from a port in California. In October, all of that equipment is sent to Antarctica as cargo on C-17 military planes. The scientific teams spend six to seven weeks assembling their payloads, preparing them to be launched from the LDB site. Here is EBEX in its beginning stages.
As the days went on, EBEX grew and grew.
Do you see that cylinder attached to the side of the experiment in the photo above? It is a star camera built by one of Michele’s students. Here is a closer look.
While teams of scientists were busy inside, other people tested the launch equipment outside. This huge vehicle, nicknamed “The Boss” after Ernest Shackleton (whose men called him that), is used to hold the payload just before it is launched. The ability to carry/lift a heavy load is critical for the launches that take place. EBEX has a scientific payload that weighs about 6,000 pounds. NASA’s equipment for the experiment adds another 2,000 pounds of electronics for communication, and support equipment for the flight. That support equipment includes the parachute, separation package, and termination package. I’ll explain those last two in a little bit.
Meanwhile, EBEX was moved outside for some testing.
The experiment was eventually covered in a layer of aluminized mylar, which protects it from the sun. I thought the experiment might get cold as it goes up into the atmosphere, but Michele told me that the danger is that equipment will get too hot from the sun. The mylar shield reflects radiant heat away from the equipment.
EBEX was moved to the wooden platform called “the dance floor” where it was tested without the interference of any other metal around. It actually does look like a regular portable dance floor.
On the day of a launch, Anne Dal Vera, who works at the LDB site, sends up a special small balloon called the pibal (pilot balloon). She does this every half hour. These balloons go from the surface to about 4,000 feet high. Anne observes the pibal with an instrument called a theodolite. It is a surveying instrument, leveled and calibrated to the direction north.
The info from the theodolite travels by cable to the rigging building, where a computer converts the information in wind speed and direction. This data is important because everyone needs to know which direction to lay out the balloon, based on the wind direction at launch time.
The balloon is inflated, using helium from large storage tanks moved out to the launch area.
The balloon is only filled to about 1% of its capacity, because it will expand as it moves up into the atmosphere. The balloons reach an altitude of approximately 113,ooo-114,000 feet above the ground. They circle Antarctica for about 10 days. At this time of year there is something called the polar vortex; winds circling Antarctica with a more regular wind speed and direction. If you check the NASA site listed below, you can see how the three balloons currently circling the continent are basically following the same pathway. You can move one image over another, and compare the paths and direction. It is very cool to do this.
The balloon gets bigger…
And finally the balloon is released to lift the payload, which has been held in place by the Boss.
Once the balloon is aligned vertically with the payload, that payload is gently released to the care of the balloon. Sometimes the Boss has to move forward or backward to adjust this take-off. The balloon looks more bulb-shaped at this point, but eventually rounds out as it climbs and expands.
I sketched out a diagram below, to give you an idea of how this all looks. It’s a rough estimate, not drawn to scale, but I think it might help you understand the whole project. The entire string of the balloon and all that is beneath it, is about 1,000 feet tall.
Once the balloon is launched, it starts to collect and send back data. Scientists can track its progress. When the experiment has circled the continent, the goal is to have the experiment land somewhere as close as possible on the Ross Ice Shelf. When the team makes the decision to land the experiment, they deploy the termination package. The balloon is ripped apart at termination and separates from the rest of the equipment. It is later retrieved on the ice shelf, along with the other bits and pieces of the project. The balloon is not a reusable item.
The parachute is automatically deployed at this point, and the payload drifts to the ground, supported by the parachute. Once the team is sure that the payload is on the ice shelf, they will deploy the separation package. This makes sure that the payload is detached from the parachute. They do not want the payload to be dragged across the ice shelf if a strong wind blows the parachute. Parachutes used for this operation are reusable.
Small planes (usually a Twin Otter to start) are sent out to recover the data first, and to assess the situation. Next, all pieces of the experiment and parachute, etc. are retrieved by plane or helicopter, and brought back to the LDB facility.
Michele told me that Antarctica is a great place to launch long duration balloon projects because balloons can be flown without disturbance, and can be flown longer than any other place in the world. The sun at this time of year can supply solar power 24 hours a day, 7 days a week. Weather is much better here at this time of year compared to other locations. No one has to ask permission of other countries to fly the balloons in their airspace; all scientific projects conducted here are approved by SCAR (the Scientific Committee on Antarctic Research).
The video clip below is quite a large file, and I hope you will be patient with it loading on your computer. It is worth it because you’ll see the balloon being launched and the payload being lifted. It is not the EBEX experiment, I think it is Super-TIGER. But it does give you the idea of how the launch would work. At one point someone’s hand is in the way, but stick with it, the payload is lifted up shortly after that part. Also note that that balloon is all of the clear/white “string” — all the way until the red part. When the balloon is fully inflated, it is as big as the Houston Astrodome.
Thanks to Michele for the interview, photos, and videos. Enjoy and talk with you tomorrow.